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F. A. McKeown

Publications and source records attributed to F. A. McKeown.

At least 19 recordsLinked to original sources
USGS1994

Evidence of contemporary and ancient excess fluid pressure in the New Madrid seismic zone of the Reelfoot Rift, central United States

In the winter of 1811-12, three of the largest historic earthquakes in the United States occurred near New Madrid, Missouri. Seismicity continues to the present day throughout a tightly clustered pattern of epicenters centered on the bootheel of Missouri, including parts of northeastern Arkansas, northwestern Tennessee, western Kentucky, and southern Illinois. In 1990, the New Madrid seismic zone/central United States became the first seismically active region east of the Rocky Mountains to be designated a priority research area within the National Earthquake Hazards Reduction Program (NEHRP). This professional paper is a collection of papers, some published separately, presenting results of the newly intensified research program in this area. Major components of this research program include tectonic framework studies, seismicity and deformation monitoring and modeling, improved seismic hazard and risk assessments, and cooperative hazard mitigation studies.

Professional Paper↗
USGS1988

Structure of the Blytheville arch in the New Madrid seismic zone

Seismic-reflection profiles across part of the New Madrid seismic zone in northeastern Arkansas and southeastern Missouri show a faulted and structurally complex zone, originally known as Charlie’s ridge but herein renamed Blytheville arch, which is about 10 to 15 km wide and about 110 km long. Several exploratory drill holes in the arch penetrate Upper and possibly Middle Cambrian formations directly below Cretaceous rocks, whereas drill holes off the arch penetrate the Cambrian and Ordovician Knox and Arbuckle Groups equivalents and possibly younger Paleozoic rocks below the Cretaceous; therefore, the pre-Cretaceous rocks in the arch are structurally high. Most earthquakes in the northeast-trending segment of the New Madrid seismic zone along the axis of the Reelfoot rift occur along the arch. Focal mechanisms of earthquakes in the trend show right-lateral, strike-slip movement. Epicenters in the northeastern part of the seismic trend between Caruthersville, MO, and Blytheville, AR, are spatially less dispersed than those to the southwest between Blytheville and Marked Tree, AR. Most of the hypocenters to the northeast cluster between 6 to 12 km deep, whereas those to the southwest range from near the surface to about 15 km deep. Earthquakes in the northeast part of the seismic trend are concentrated along a fault zone under the arch, whereas those to the southwest are more dispersed under the arch. A seismic trend that extends south-southwest from near Charleston, MO, projects to the northwest side of the ridge near Blytheville, where the seismicity changes character and the southeast boundary of the arch trends more easterly. The relationship between the structural boundaries of the arch and the seismicity may establish the extent of part of New Madrid seismicity and improve the basis for seismic hazard assessment.

Arkansas, Kentucky, Missouri, Tennessee↗
USGS1983

Summary of workshops concerning regional seismic source zones of parts of the conterminous United States, convened by the U.S. Geological Survey, 1979-1980, Golden, Colorado

Workshops were convened by the U.S. Geological Survey to obtain the latest information and concepts relative to defining seismic source zones for five regions of the United States. The zones, with some modifications, have been used in preparation of new national probabilistic ground motion hazard maps by the U.S. Geological Survey. The five regions addressed are the Great Basin, the Northern Rocky Mountains, the Southern Rocky Mountains, the Central Interior, and the northeastern United States. Discussions at the workshops focussed on possible temporal and spatial variations of seismicity within the regions, latest ages of surface-fault displacements, most recent uplift or subsidence, geologic structural provinces as they relate to seismicity, and speculation on earthquake causes. Within the Great Basin region, the zones conform to areas characterized by a predominance of faults that have certain ages of latest surface displacements. In the Northern and Southern Rocky Mountain regions, zones primarily conform to distinctive structural terrane. In the Central Interior, primary emphasis was placed on an interpretation of the areal distribution of historic seismicity, although geophysical studies in the Reelfoot rift area provided data for defining zones in the New Madrid earthquake area. An interpretation of the historic seismicity also provided the basis for drawing the zones of the New England region. Estimates of earthquake maximum magnitudes and of recurrence times for these earthquakes are given for most of the zones and are based on either geologic data or opinion.

Circular↗
USGS1980

Recurrent intraplate tectonism in the New Madrid seismic zone

For the first time, New Madrid seismicity can be linked to specific structural features that have been reactivated through geologic time. Extensive seismic reflection profiling reveals major faults coincident with the main earthquake trends in the area and with structural deformation apparently caused by repeated episodes of igneous activity.

Arkansas, Illinois, Kentucky, Missouri, Tennessee↗
USGS1978

Hypothesis: Many earthquakes in the central and southeastern United States are causally related to mafic intrusive bodies

Assessment of earthquake hazards in the United States is based largely upon knowledge acquired in the seismically active parts of the western United States. Earthquakes in the central and southeastern United States are seismologically and geologically very anomalous, however, compared with those in the western United States. For example, shallow earthquakes of magnitude 7-f in the western United States in general have tectonic surface faulting associated with them. No tectonic surface faulting, however, has been found to be associated with the New Madrid, Mo., earthquakes of 1811 and 1812, several of which had estimated magnitudes of 7-f. The lack of surface faulting is, in part, responsible for the fact that the New Madrid earthquakes have not been related with certainty to any particular geologic structural element, which makes assessment of the seismic hazards associated with possible similar future earthquakes very difficult. Geologic and seismologic data from the central and southeastern United States, however, suggest a spatial correlation between mafic intrusive rocks and seismic activity. An additional supportive correlation is that the trend of many dikes coincides with the trend of nodal planes in many fault-plane solutions. These correlations differ greatly from the direct correlation of earthquakes with faults in the western United States. Consideration of different concepts of earthquake sources in the central and southeastern. United States seems necessary- The preferred concept is that local high-stress concentrations, which may result in earthquakes, occur at or close to the contact of mafic intrusives and their felsic host rocks. Ancient rift zones may have been the primary control of the location of the mafic intrusives. Implications of a causal relation between mafic intrusives and seismicity are that more useful seismo-tectonic maps may be possible and that the source dimensions of the earthquakes would be small. Because of low attenuation, however, effects of earthquakes in the central and southeastern United States, even if relatively small because of smaller source dimensions, must be considered hazardous.

Journal of Research of the U.S. Geological Survey↗
USGS1969

Summary of geologic effects of the Boxcar event, Nevada Test Site

A high-yield underground nuclear explosion at the U20i site, formed a sink 1,000 feet in diameter above the explosion point. Fractures opened as far as 20,000 feet from the explosion and rock-falls occurred as far as 15 miles. Most fractures were coincidental with north-trending naturally occurring faults. Maximum displacement along a fault was 3 feet vertically with the downthrown side the same as that on the original fault.

Nevada↗
USGS1962

Interim geological investigations in the U12e.04 tunnel, Nevada Test Site, Nye County, Nevada

The Ul2e.04 tunnel is a part of the Ul2e tunnel system, which has been driven southwestward beneath Rainier Mesa in the northern part of the Nevada Test Site. The Ul2e.04 tunnel was driven about S. 15? W. in zeolitic tuff of subunits E and F of Tunnel Bed W near the top of the lower member of the Indian Trail Formation (upper Miocene or lower Pliocene). Dolomite of Paleozoic age lies about 915 feet below the end of the tunnel; vertical cover over the end of the tunnel to the surface of Rainier Mesa is about 1,390 feet. The tuffs in the tunnel strike almost north-south and dip to the west. There are several normal northwest-trending faults with vertical to steep dips and small displacements. The predominant joint set strikes northwest and dips mostly vertically or steeply to the northeast. Petrographically and chemically the tuffs in the U12e.04 tunnel are similar to other tuffs of the Indian Trail Formation from the Nevada Test Site, The tuffs in the tunnel have an average porosity of 38.6 percent, dry bulk density of 1.46 g/cc (grams per cubic centimeter), grain density of 2.38 g/cc, water content of 20.7 percent by weight. Shore hardness of 25.1, and unconfined compressive strength of 4,400 psi (pounds per square inch). Separately, the tuffs from the chamber at the end of the tunnel have an average porosity of 36.8 percent, dry bulk density of 1.51 g/cc, grain density of 2.38 g/cc, water content of 20.0 percent by weight, Shore hardness of 27.2 and unconfined compressive strength of 4,500 psi. An NX-size cored hole was drilled from the surface of Rainier Mesa into the Ul2e.04 chamber.

Open-File Report↗